A preferred use for equipment of this type for transporting goods or products occurs in situations where goods have to be brought to an inspection apparatus for their examination. This can be a weighing system for the dynamic weighing of the goods passing over it, or a device for the detection of metallic contaminants in products, or an X-ray apparatus for the detection of different types of foreign matter in products, as well as other inspection equipment. Preferred applications are for products in the form of prepackaged goods in the food industry or in the pharmaceutical industry, particularly powdered or fine-grained prepackaged products.
A belt conveyor within this context can be, for example, an infeed conveyor, an outfeed conveyor, or a weighing conveyor for in-motion weighing on a dynamic weighing device. Likewise, belt conveyors for transporting products through an inspection system for the detection of contaminants are to be considered within the present context. A conveyor belt is in many cases configured as a so-called endless belt, meaning a belt that forms a closed loop, which runs around at least two belt rollers, specifically a passive idling roller and a driven roller which is connected to a drive mechanism which actively drives the movement of the belt.
As an example for the goods or products to be transported, packages containing powdered or granular substances should be mentioned here, with sugar being of particular interest. Sugar that is to be sold in retail stores is packaged in units of a predefined weight, for example 1 kg, preferably in paper packages. These paper packages are normally folded paper bags which are glued at the closure seams and which firmly encase the contents as a package. As is known from experience, these paper packages are not completely leak-proof, and in the course of transportation it has to be expected that granules of sugar may escape in some small amounts from the paper packages at any time and remain lying on the transport conveyor. However, such granules of sugar lying loosely on a conveyor belt can cause enormous damage, if they enter between the movable parts of the belt conveyor mechanism.
Powder or fine-grained material lying on the conveyor belt creates the problem that these materials are easily spread around by the rapid movement of the conveyor belt and can thus also get under the belt, for example onto the inside of the endless loop, where they are ground up, and that they can end up entering into the bearings of the conveyor rollers that are located at the ends of the belt conveyor. There, they can cause serious damage as they heat up, become compacted and clogged together, and as a result the affected components of the belt conveyor will have to be exchanged frequently.
Due to the open construction of the belt conveyors of the known state of the art, there is furthermore the risk that the material lying on the belt could get into the drive mechanism. This danger exists in particular in the case of a belt drive which normally includes a belt running over two pulleys, such as a toothed belt, a V-belt and the like. The powder or fine-grained material can be carried from the belt to the pulleys, where it can become compacted and form a deposit. This leads to an accumulation of material at the circumference of the pulley and as a consequence, an increase in belt tension, whereby the belt is stretched to the point where it will ultimately break. The failure of a belt and especially the time needed to replace it also means unproductive downtime for the entire system involved.
According to state-of-the-art solutions that aim to counter this problem, the packages are in many cases transported on a multi-strap conveyor instead of a belt conveyor, wherein a catch basin is arranged below the conveyor straps to collect the material leaking out of the packages. However, this arrangement still does not ensure that the for the most part openly exposed bearings will not be reached by the escaped material. There is further the danger, particularly at high operating speeds, that vibrations of the straps could disturb the smooth running of the conveyor, a condition that will manifest itself through an inaccuracy of the measurements, for example in the dynamic weighing of the products.
A different solution is proposed in DE 10 2006 048 251 A1, wherein the conveyor belts or conveyor ribbons are guided along both lateral borders in a precisely fitting guide channel. The purpose of this measure is to prevent small particles of the transported materials from falling into the space below the belt.
Another solution is disclosed in EP 1 2821 941 A1, wherein a conveyor device for weighing applications is described. An endless belt, which is looped around rollers, is designed with a greater width than the length of the rollers. In the laterally overhanging border areas along both sides, the belt has ledges protruding downward, i.e. towards the inside of the closed loop. These protruding border ledges are in contact with the two opposite-facing end surfaces of the rollers. In addition, there are side plates positioned next to the opposite-facing end surfaces of the rollers, which together with further plates that are arranged below the conveyor belt are forming a kind of conveyor bed to support the conveyor belt. The outside plates have setbacks along their edges, which are likewise engaged by the protruding border ledges of the conveyor belt. Thus, the conveyor belt has a guiding constraint which prevents lateral fluctuations in the movement of the belt.
The invention has the objective to make a lasting improvement—without the use of a guiding constraint—in the breakdown vulnerability of a conveyor, specifically a belt conveyor, which is caused by pulverous or fine-grained material leaking out of the containers being transported, in order to prevent downtime of the entire system.